This invention relates to a screw gun and method for loading and inserting screws. There is a need in industry for a screw gun which can load and insert a plurality of screws without a worker having to individually handle each screw. The screw gun should be compact, lightweight and easy to use in the field. Specifically, for example, in the heating, ventilating and air conditioning (“HVAC”) industry, hex-head self-tapping screws with integral washers, sometimes known as “tech screws”, are used for connecting adjacent sections of sheet metal duct. A majority of the time, the task of connecting these adjacent sections of sheet metal duct occurs on lifts and in confined spaces. An HVAC worker will insert anywhere from about 2 to 10 screws per duct joint. The present method used by the HVAC worker to insert a tech screw involves the use of a drill with magnetic hex socket in the drill chuck and an apron full of tech screws. The HVAC worker must pick up an individual tech screw from his apron. He then by hand places the screw into the hex socket, and then inserts the screw through the sections of duct. The process is made more difficult when the worker wears gloves, not uncommon in this industry. It is estimated that up to 30% of the screws intended to be inserted into sheet metal duct sections are dropped and lost by the worker as he or she attempts to hand place a screw in the hex socket. Thus, the present method is laborious, slow and costly. Accordingly, there is a need in the HVAC industry, and other similar industries, for a lightweight, portable screw gun that will increase the productivity of workers and decrease costs associated with the time consuming manual insertion of screws in the gun and the cost associated with lost screws.
Screw guns for feeding and locating fasteners for insertion into a workpiece are generally known in the art. However, these designs are not practical as they are overly complex and, therefore, costly, and they are bulky and not easy to use, especially when working in confined spaces. For example, known power operated devices for feeding and locating fasteners, like those disclosed by U.S. Pat. No. 5,031,489 to Young et al. and U.S. Pat. No. 5,015,127 to Hockman, require that a fastener driver be connected to an air supply to power the device and connected to a hopper or the like in order to continuously feed the driver with fasteners. Such devices limit their application because of their lack of mobility and unwieldiness. Accordingly, such devices are not practical for use in confined spaces, such as when working on a scaffolding or a lift. Similar devices for feeding and locating fasteners have strips which carry the screws and are swingedly suspended from the device, such as disclosed in U.S. Pat. No. 3,910,324 to Nasiatka and U.S. Pat. No. 4,581,964 to Takatsuru. These devices are also not practical for use in confined spaces because of the added weight and awkwardness associated with the devices.
U.S. Pat. No. 4,936,169 to Parsons discloses a portable device for positioning and inserting fasteners wherein an applicator is positioned adjacent to a positioning mechanism containing a rotatable cylinder which includes a plurality chambers for housing fasteners. However, the Parsons device also includes a number of drawbacks including that it is bulky, the operator is required to align a screw with the applicator by hand before he can insert a second screw into a workpiece, and the screw is not readily visible prior to insertion.
The present invention solves the problems of the prior art devices as discussed hereafter.